Method and apparatus for rolling disks



A g- 1932- c. L. EKSERGIAN ET AL 3 3 Filed Dec. 51. 1929 Sheets-Sheet 2i FISH l N VIS .X' 'I'Oh 5, EDWAQD GBUDD. m' CAROLUS LEKSERGIAN W .'u'myl JFE?:

xx A A wz a 5 a mw s atented Aug. 2, 1932 NITED STATES PATENT OFFICECAROLUS LEVON EKSERGIAN,

'WEEEL COMIPANY, OF

PHILADELPHIA, PENNSYLVANIA, A. CORPOBATION OF PENNSYLVANIA BIETHOD .ANDAPPARATUS FOB ROLLDQ 'G DISKS Application filed December 31, 1929. seralNo. 417,613.

The outstanding object of our invention is to achieve an improvement inthe rolling of relatively thin tapered disks of the nature of automobiledisks, particularly an improvement in the forming of such disks byobtuse anglo dies from billets of substantially cylindrical form such ascan be most cheaply supplied from hot bar stock. Dsks of this order areof such thinness that their cross-section has a thickness but a fractionof the crosssection of relatively heavy disks such as used in carwheels. These relatively thin disks possess a lightness and anadaptation to forming by die stamping, and ultimate resiliency andresistancetodistortion in marked contrast to the heavy massive disk-likebodies of car Wheels. Such disks have today a trenendous market not onlyas automobile wheel disks per se, but also as brake drum disks, brakedrum covers, ete. Our invention partakes jointly of the nature' of amethod and apparatus From one point of view, an outgrowth of the oneappears bound up in the other. Together they not' only result in animproved disk over former methods and apparatuses, but valso in agreatly enlarged range of adaptation of the obtuse angle process ofrolling such disks.

It has been found that when the obtuse anglo process is used to producerelatively thin disks of the natue of automobile disks, if the reductionis extreme`anel the more especially where the disk is a tapered disk,rather than one'of uniform section as in the case of disks for brakedrum formation, the more especially also Where it has been sought toreduce a disk with a relatively thin center or with no center at all, adisk independent of hub structure rather than a disk integral with suchstructure there results inordinate reduction 'of section of the innermarginal zone of the disk, and sometimes actual rup-- ture of the metal.This occurrence has heretofore prevented the general application of theprocess to all forms of relatively .thin disks of the nature ofautomobile disks. The range of the process as practiced has thereforebeen limited. Our invention removes, these limitations. p r

It has also been found that with certain forms of obtuse angle diesthere results an irregularity or sometimes a broken or sharply deflectedor a distorted or twisted, flow of metal; and that while the rolledsection itself is perfect, the directionof such flow is contrary or atan anglo to that direction which it should follow to attain maximumstrength and best drawing qualities in the resulting product. Ourinvention tremendously improves the general direction of flowirrespective of the particular form of the dies being used.

The cause of these difliculties which our invention has overcome we donot clearly understand. Different angular velocities of complementalportions of dies, misalignments, temperature difi'erentials betweeninner .and outer zones (the outer and more expansive cool more rapidlythan the inner zone, especially in contact with the cooler outerportions of the dies and-therefore have greater strength), and theangular direction of the rolling enlarging the circumference at agreater rate than radial flow can efiectually follow, are amon thecauses. Sometimes one alone may be e ective, at other times several orall of them may be effective, in conjunction with or without others. Butwhatever the causes are, the efl'ects are found to be removed by ourmethod and apparatus.

According to our method, while the blank is being rolled in the obtuseangle dies, we maintain a central cross-section' of metal in- OFDETBOIT, MICHIGAN, .AND EDWARD G. BUDD,` OF PHILADELPHIA, PENNSYLVANIA,ASSIGNORS TO BUDD dependently of the main body of the disk, and

of a thickness considerably greater than the .thickness of the mainbody, and'simultaneously express metal from the center ofthe blankoutwardly by way of this increased cross-section, and along lines whichare graduall and smoothly converged into the metal of t e main body ofthe disk. Obtuse angled rolling, as well known,- is by simultaneous'axial compression and circumferential rolling on a line extendingradially outwardly vfrom the center or inner periphery to the outerperiphery of the blank. The thickened cross-section of metal which wemaintain in wardly of 'the'inner eriphery or main body of the disk ispreferably of a structural form unrelated 'to tle main body; of thedisk,

one-half.

though it may be so related if desired. It is thereafter reduced torelated form, or carrying the reduction to the extreme, is removedaltogether from the main body.

T e apparatus is simple. It consists of an obtuse angle die having acentral boss, an adjoining depression, and an outwardly disposed mainbody, which latter is complemental to the face form of the resultingproduct desired, and which central boss and adjoining depression aresinuous in form with the walls of the depression merged smoothly andunbrokenly along converging lines into the walls of the main body of thedie. Preferably each of a pair of obtuse angle dies is Similarly formed,but this is not necessarily so, and there are a wide range of variationsbetween the embodiment of one or all of these features on the one diewith none of them on the other and the distribution of these featuresbetween the faces of a pair of obtuse angle dies.

The drawings illustrate both the apparatus and the method.

Fig. 1 is a transverse cross-section of a pair of dies embodying ourinvention in each of which its features are constructed, and a freshblank just inserted.

Fig. 2 is a similar cross-section showing a fresh blank in position tobe operated upon, and the operation just started.

Fig. 3 shows the operation when the axial length of the blank has beenreduced about Fig. 4 is a simlar cross-section showing i the operationalmost completed.

Fig. 5 shows the operation completed.

Figs. 6 and 7 are axial cross section of a re-press used in forming ofthe blank for the rolling Operations and of the blank formed by it.

Fig. 8 is a great enlargement of the central portion of Fig. 1.

spectively. Wit

dlg. 9 shows a finally completed hubless Figs. 10 and 11 are the opposeddies. The zone 12 constitutes the main body of the die in each case. Itsface is complemental to the face of the finished product. Within thezones 12 and immediately adjoining them are zones 13 constituted bdepressions 14 and 14 rein the 'zone 13 are zones 15 and 15' constitutedby bosses 16 and 16' respectively. The walls of the' bosses 16 and 16'and the adjoining depress'ions 14 and 14' are P of approximately sinuousform merging smoothly one into the other, and the walls of depressions14 and 14' are in turn merged smoothly and unbrokenly, still in sinuousform into the main body of the dies in zones 12. A As shown, each die isso formed and as above stated, each or all of these features may beembodied in either die or various combinations of the same.

The blank 17 to be rolled is formed from a cylindrical billet 18 cutfrom hot bar stock by means of the re-press mechanism shown in Figs. 6and 7. The auxiliary reciprocable dies 19 and 20 of this pre-pressapparatus when they close in on each other along the axial line 21 asshown in Fig. 6 and finally approach each other to the extent shown inFig. 7 impart to the billet 18 the substan: tial ball shaped form of theblank 17, and on the axis 21 provide opposed spherical cavities 22. Themethod and apparatus for re-pressing the billets 18 into the form ofBlank 17 is described fully in the co-pending application SerialNo.403,402 filed October 30, 1929. Sulfice it to say here that thespherical centering cavities 22 formed by dies 20 constitute preliminarycentering formations for the obtuse angle rolling formations while thegeneral convex ends 23 of the blank constitute final centeringformations for the rolling operation.

- The ball shaped blank 17 so formed is end tered into the obtuse angleddies of Fig. 1 by placing the axis 21 of the blank in approximatecoincidcnce With the axis 24 of the relatively fixed obtuse angled die10 and approaching the ward the die 10 until the blank 17 is engaged inits spherical preliminary centers 22 by the bosses 16 and 16' associatedwith the respective dies 10 and 11. The advantage of the spherical shapeis that there is accurate fitdie 11 along its axis 25 toa ting of thecomplementally shaped spherical the center areas of its ends are ofconvex surface contour approximating so nearly as general conditionswill permit a ball shape. Such shape precludes the formation of folds inthe surface of the disk during rolling. The corners 27 of thepre-pressed billet through which the convex sides 28 are merged into thecentering and Sections 22 are very steep. This has a two fold advantage;first in securing the very strongest centering comonent of forces as thedies approach each other, the major portion of the axial pressure. beingthereby translated into a centering force. and secondly, in providingthe most easy flow of the metal under this strong force and the stillstrenger rolling force to the more perfectly fill the cavities 14 of thecentering zone 13 of the dies. Conplemental relative shaping of thecentering zone 13 of the dies is at a slightly greater acute anglebetween the tangents 30 to the exterior corners 31 of the centering zoneandthe axis 21. Relatively locating the corners 27 of the centering zoneof the billet with respect to the outer corners 31 of the centering zoneofthe dies is substantially interiorly thereof whereby strong initialcentering grip is assured. This is more than merely making the centeringend of the blank similar in form at the outer corners 27' and inwardlyof the centering zone 13 of the die in that it involves a radialdistance 32 to the corner 27 of the prepressed billet less than theradial distance 33 from the axis 2 1 of the fixed die to the corner 31of the centering zone 13 of the angularly disposed adj'ustable axis die.

In the initial approach of the dies 10 and 11 toward each' other,centering pin 16 of movable die 11 is forced back to the position shownin Fig. 2 against yielding pressure and a stop. The blank ispreliminarily centered through the axially disposed depressions 22 freeof contact with the major centering zone 13 of the angularly adjusteddie. This is for the reason that until the final centering surface 23has been completed by the forging and rolling operation its engagementwould preclude or destroy accurate centering by the preliminarycentering surfaces 22. It is to this end the centering pin 16 of theadjustable die when the dies are open is yieldingly held forward of itsposition durng rolling.

In this final centering operation the axially disposed sphericaldepressions 22 in the billet are sutficient to keep the billet centeredaccurately against the initial outward forces set up by the acute angledcorner formations 29 and 31 in producing the completed final centeringsurfaoes 34: on the ends of the billet. Modification of final centeringsurfaces 23 is shown as set in in the approach of Fig. 2. The axialdepressions 22 might well be in-- sufiicient, and probably in most casesare insuflicient, to center the billet during the further rollingOperations. In fact, in 'most cases in the last stages of rolling theaxial center of the disk is very materially reduced. The product isctered entirely upon the greater end areas of the zone 13 surroundingits ends. From this standpoint, the method comprehends the formation ofminor and preliminary centering surfaces 22 on the axis of the billet,by pre-pressin'g, the initiation of major and final centering surfaces23 on the billet by pre-pressing, completion of such major and finalsurfaces to the form 34 by the initial forging and/or rolling operation,together with a-transfer of the centering formation during rolling fromthe axial reliminary centers 16 substantially or entirely to the finalcenters of the zone 13 surrounding, a transfer of seating from the axisto the end peripheries of the blank.

Further axial compression being applied to the dies 10 and 11 androlling being started either simultaneously with the further compressionor an appropriate time thereafter, the blank is very quickly reduced tothe shape shown in Fig. 3, after which the reduction of the blank towardits final form is accomplished more by rolling and less by compression,though the compression is maintained as an incident to the rollingrather than a principal factor in the formation. Rolling rapidly furtherreduces the section to the form shown in Fig. 4 where the productassumes a disk-like form, relatively thick and of the order of railwaycar wheel thickness. From this point the disk is reduced toward and intothe degree of thinness commonly found in disks of the nature ofautomobile wheel disks, relatively very thin, very light, and most timestapered in thickness from center or inner periphery to the outerperiphery. The full reduction is shown in Fig. 5.

Throughout this operation through the use of the depressions 14 we havemaintained a thickness of cross section at the center of sufficientcross-seetional area so that the resulting stresses will not besuflicient to cause rupture or undue lateral straining of the variousportions of the blank and irrespective of other causes tending to reducethe section of or to rupture the blank in the neighborhood of the innermargin of the Zone 12 of the main body. This thickness we adjust byappropriate trial and error, or by calculation as may be most convenientto accomplish our aim. Preferably we maintain a thickness somewhat inexcess of that sufficient for the purpose to allow for a margin ofsafety.

The flow of the metal during the rolling operation takes place throughthe throat 37 formed by the endmost sinuous sections'of the `dies, wherecentering zone 13 ends, fed from the mass of metal within thecomplemental cavities 14 of the centering zone 13. This mass 36 of metalis of such cross sectional thickness as against the cross sectionalthickness of the center 35 of the blank that starving exteriorly thereofis precluded and is confined to 'the central area of the blank withinthe portion 36 of the thickened cross section. The thickened section 36also retains the heat better than a thinner section and guaranteesregular and consistent flow through the throat 37 under the force set upby the increasingly greater enlargement of diameter progressivelyoutward from the center. Still further, the massive centering action ofthe section 36 as' progressively derived from the massive end portionsof the 3 metal and their continued approach toward each other noreclosely than the walls of the adjoining depression 14 and 14' causes aflow of the mass of metal at the center of the blank and in theadjoining margins of the mass within the depression 14 and 14', radiallyoutwardly along smoothly converging lines indicated by the arrows 18into the main body of the disk. Smoothness and regularty of the lines offlow is therefore cnforced under the expressin action and by theappropriate shaping o the walls of the boss 16 and the depresson 18.This enforced and controlled action greatly augments the action of theexcess cross-section of the zone 13 in maintaining strength and stillfurther widens the range of adaptation of the obtuse angle rolling millto fabrication of relatively thin disks and the like.

A feature of the method includes starving of the axially disposed'centers of the disk. This is deliberately brought about by the ini tialprovision of the axially disposed spherical centering cavities 22, andtheir subseuent naintenance by the complenentally isposed sphericalcentering pins 16 and 16' of the dies, which pins 16 are fixed relativeto the dies after complete centering and are approached toward eachother at the same rate as the dies. Thereby the center of the billet isaxially always the thinnest and radial strength incident to rolling uponthe billet least at this point. Starving in all regions radially removedfrom the center is therefore effectually precluded.

l`he rolling; having been completed to the stage shown in'Fig. 5, thedies are then raised from each other and the product removed from themachine. Thereupon fixed center portion 36 within the zone 13 of thedies is removed by a blanking operation and the hublcss disk of F ig. 9becomes the inal project.

If desired the removed mass of metal 36 may be subjected to furtherOperations to form hubs per se or other articles. Indeed, throughappropriate modification without departing from the generic spirit of myinvention the portion may be given the form of forged ring or hub, or atleast, the form which is transmutable into such construction by efii'-cient and economical subsequent Operations.

Summarizing in part, it will be noted that in the carrying' out of theprocess the bosses or pins 16 projecting: from the faces ofthe diesafford the initial or preliminary centering, and that after thecentering is taken over by the walls of the depressions 14 and 14', theyno longer have this function except in a subordinate way and foraportion ofthe rollingperiod. In fact, as the final major centering istaken over by the walls of the depressions 14 and 14' the axis 21 of thebillet 17 is approached more and more nearly to the axis 24.- of themale die 10. The starving of the center incident to the radial flow ofthe mass material likewise relieves the bosses 16 and 16' of thiscentering function. Yet while they are relieved of this centeringfunction, they progressively take on another important function, that ofcoring out and interiorly rolling the center of the mass prior to andduring such starving as may occur dependiig upon the mass condition,this coring out comes about by the rolling action interiorly of thecored part as clearly appears in F igs. 4 and 5, particularly on thepart of the boss 16' of the female die.

Relative proportions of the male and female dies should also beespecially noted.

'The depressions 14' in the face of the female die are much deeper thanthe corresponding depressions 14 in the face of the male die. Therebythe radial pushing out of the central mass of metal is aided rather thanretarded. On the other hand, the deeper depression in the female dieinsures sufficient hump at the center section to guarantee ade uatecentering in the presence of the angu arity of the female head 11.

The contour of each die and the relative contours of the dies 10 and 11have a definite relation to the volume of material of the billet 17. Ifthe fiare of the walls of the depressions 14 is not sufiiciently largefor a given volume of material, a flash will result between the twodies. This is intimately related with the shape of the billet 17 Aspreviously emphasized, the shape of the billet and the shape of thedepressions conjoin to prevent the formation of slivers or cold cracks.Thus, it is seen that the relation between the shape of the dies and theshape of the billet is an intimate one, intinately a part of our generalprocess. The shape of the billet is not only one which can be rolledwithout the development of adverse factors as outlined in thisspecification, but also one which can be pre-pressed effectively andefiiciently. It is not only one which can be effectively centered in therolling dies but also one the centering portions of which can beeffectively developed in the pre-press. Still further back, thecentering formations on the ends of the billet, both the preliminary andthe final, are formations which can be readily effected from a blankhaving its ends in the convergent planes as shown in Fig. 6. Theseconvergent planes'are in turn formed by the cut-off knives. The cut-offis achieved by the process and apparatus described in the copendingapplication of C. L.- Eksergian and William A.` Weightman, 'filedOctober 18, 1929, Seri'al No. 400,480.

L. Eksergian and William AWeightman, filed October 30, 1929` Serial No.403,402.

Especial note should be taken of the functions of the central mass ofmetal during the rolling operation. As has appeared, it initially servesas a massive centering means Pre-pressing is *achieved by the apparatusand method described in the co-pending 'application of C.

' efiectually flow. The coring econte guaranteeing concentricity ofrolling under the extremely heavy radial strains. Such massive centeringmeans are the more effective by reasons of the high temperature andgreater plasticity of the central mass as distinguished from the lowertemperature and less plasticity of the ever thinning disk portion of theblank. While`the relation between stress and strain is not constant withplastic flow, the radial stresses are very marked and become the morecritical as the thinning of the disk proceeds. The metal rolling of theobtuse mill is, of course, an annular rolling in the circumferentialdirection. The displaced metal results in a greater annular orcircuniferential dimension by direct addition to the length of any givencircle of rolling. By reason of this, there is progressive perimetralenlargement and by the same token, progressive dimensional enlargementof each Circular element of the entire disk surface. The radial movementof the material being rolled is therefore primarily a. function of thedirect cir-' cumferential or tangential travel of the material producedby the rolling action. The central mass of metal provided according toour process by the contouring of the dies described, particularly thedepressions 14, establish an equilibrium of radial flow under theseconditions with the natural center feeding of the material. In otherwords, as the inner peri hery of the disk-like body being rolled ten sto enlarge in circumference, material is drawn from the center mass tomaintain its dimension and to relieve it of undue stresses incident tothe tendency to enlarge under the radial strains. The axial compressionof the central mass adds this radial compensating and equilibriummaintaining out action of the pins which roll the inner surface of thecored out hollow of the mass assist this same action. The rolling actionof the pins or bosses 16 and 16" is virtually an internal rolling. By

all of these actions the material is expressed radially from the'central mass. Equilibrium is established between the radial forces setup by axial compression and the coring out action and the pulling radialforces induced by the circumferential rolling. The resultig radialoutward flow is stimulated by the a vantageous sinuous sections of thedies which set up good flow lines for the central metal mass. However,the important function of cntering first mentioned, as performed by thecentral mass of metal in coaction with the complemental die formation,necessitates a compromise between ideal flow lines and ideal centering.The form of dies we have disclosed constitute one of the best suchcompromises now known to us.

According to our method, we regulate the axial thickness of the centralhub or hub-like mass particularly at the throat between the disk-likeportion to effect an annual cross sectional area in the throatsufficient to give enough strength to more than compensate for thereduced tensile strength incident to the higher temperature of the.central mass and the thicker portions of the threat. All starving,reductons of section, tearing and other irregularities in this regionare thereby efi`ectually prevented.

The scope of our invention is the purview of its generic spirit asdetermined by the prior art rather than the circumstantial terminologyof the foregoing specification and the anneXed claims. This isespecially true in view of the fact that it is without doubt susceptibleto considerable'modification and to embodiment in other forms than thatdisclosed herein.

What we claim is v 1. The method of rolling relatively thin disks suchas automobile wheel disks which consists in simultaneously axiallycompressing and radially rolling the blank, the while maintaining anexcess of metal of substantial thickness at the center of the blankintegral with the body thereof, and continuously feeding metal outwardlyfrom the center 'to prevent reduction of section incident to the radialstresses incident to the relatively extreme thinning. n

2. The method of rolling relatively thin disks of the nature ofautomobile disks and the thinness of which commences in a zoneoutwardlyof the center of the disk which consists in simultaneouslyaxially compressing and circumferentially rolling the blanks, the whilemaintaining at the zone where the thinness commences, a, cross-sectionof metal integral with the main body of the disk maintaining asubstantial depth of metal at the center of the blank and continuouslyfeeding metal outwardly from the center to prevent reduction of sectionincident to the radial stresses set up by the operation.

3. The method of rolling relatively thin disks of the nature ofautomobile disks and the thinness' of which commences in a zoneoutwardly of the center of the disk which consists in simultaneouslyaxially compressing and circumferentially rolling the blanks, the Whilemaintaining at the zone where the thinness commences, a cross-section ofmetal integral with the main body of the disk and of sufiicient depth toprevent reduction of section incident to the radial stresses set up bythe operation, and smoothly flowing the metal from the maintainedgreater depth of cross-section toward and into the main body of thedisk. i

4. The method of rolling relatively thin disks of the order ofautomobile wheel disks which consists in simultaneously axiallycompressing and circumferentially rolling on a radius extending fromcenter to periphery of a blank, and the while radially expressing metalat the center considerably in excess o to the main body on lines of flowmergng smoothly into the main body.

5. The method of rolling relatively thin disks of the nature ofautonobile wheel disks which consists in simultaneously axiallycompressing and circumferentially rolling blanks and the whilemaintaining a cross section o the cross section of the main body of thedisk, radially expressing the metal from the center of the blank throughsaid cross-section into the main body of the disk, and flowing saidexpressed metal on converging lines smoothly into the main body.

6. The method of rolling relatively thin disks ofthe nature ofautomobile wheel disks which consists in simultaneously axiallycompressing and circumferentially rolling on a radial line from centerto periphery of a blank, the Whilemaintaining cross-section at thecenter structurally unrelated to the final production and ofsufiiciently greater thickness to prevent reduction of cross-sectionincident to radial strains of the operation, and after the operation iscomplete, removing the said structurally unrelated central crosssection.

7. A die for rolling relatively thin tapered disks in an obtuse angledrolling mill, which die comprises an outer zone substantially of a faceform complemental to the main body of the disk to be rolled, and arecessed inner zone of a depth sufficient to provide a crosssection ofmetal of an aggregate radial strength in the rolling area sflicient toresist reduction of section under radial strains.

8. A die for rolling relatively thin tapered disks in an obtuse angledrolling mill, which die comprises an outer zone substantially of a faceform complemental to the main body of the disk to be rolled, and arecessed inner zone of a depth suflicient to provide a crosssection ofmetal of an aggregate radial strength in the rolling area suflicient toresist reduction of section under radial strains, and the walls of whichrecessed inner zone are smoothly and gradually merged into the outerzone. 4

9. A die for rolling relatively thin tapered disks in an obtuse angledrolling mill, which die comprises an outer zone substantially of a faceform complemental to the main body of the disk to be rolled, and arecessed inner zone of a depth sufiicient to provide a cross-section ofmetal of an aggregate radial strength in the rolling area sufficient toresist reduction of section under radial strains, together with anaxially arranged coring out boss.

10. An obtuse angled die for rolling relatively thin tapered diskscomprising a centrally locatedaxially extending boss, an adjoiningdepression and a main body outwardly of the depression, the boss and thedepresf body of f tal to the main body of the disk to be rolled,

Sion bein of sinuous form and merged unbrokenly into the main body.

11. An obtuse angled die for rolling relatively thin tapered disksembodying an axially located coring out boss of sinuous crosssection.

12. An obtuse angled die for rolling rela tively thin tapered diskscomprising a main a face form substantially complemenand a centraldepression of sinuous form merging unbrokenly into the main body of thedie.

13. Die structure for rolling thin disks comprising a die having a mainbody portion complemental to the shape of one side of the ultimate disk,a depression of substantial radial extent and smooth contour at thecenter of the die and a coring pin of considerably smaller radial extentthan said depression arranged centrally within the depresson.

14. Die structure for rolling thin disks comprising a die having a mainbody portion complemental to the shape of one side of the ultimate disk,a depression of substantial radial extent and smooth' contour at thecenter of the die and a coring pin of considerably smaller radial extentthan said depression arranged centrally within the depression, saidcoring pin being reciprocably mounted within said die.

15. A die assembly for rolling thin disks including, a male die, and afemale die structure comprising a die having a main body portioncomplemental to the sha e of one side of the ultimate disk, a. depressonof substantial radial extent and smooth contour at the center of the dieand a coring pin of considerably smaller radial extent than saiddepression arranged centrally within the depression.

16. The method of rolling thin disks which comprises rolling the outerperipheral portions of a blank, expressing metal outwardly from acentral portion of the blank during the rolling operation andmaintaining a constricted throat of smooth contour between the saidcentral portion and' the outer peripheral portions to restrict the flow'of metal under such expressing action.

17. The method' of formin thin disks which comprises pre-pressing aillet to form concavities in the opposite ends thereof, placing saidbillet between a air of rolling dies, initially centering said billetbetween said dies by means of bosses centrally located with respect tosaid dies, simultaneously coring the central portion of the billet androlling -the outer peripheral portions thereof and restricting the flowof metal outwardly during the coring and rolling operation.

18. The method of forming thin disks which comprises pre-pressing abillet to form concavities in the opposite ends thereof, placing saidbillet betwen a pair of rolling dies, initially centering said billetbetween said dies by means of bosses centrally located with respect tosaid dies, rolling the outer peripheral portions of the billet togradually thin the same and restricting the flow of metal outwardlytoward the periphery of the disk during the rolling operation by meansof a concavity formed in one of said dies.

19. The method of forming thin disk Which comprises pre-pressing abillet to form concavities in the opposite ends thereof, placing saidbillet between a pair of rolling dies, initially centering said billetbetween said dies by means of bosses centrally located with respect tosaid dies, rolling the outer peripheral portions of the billet tograduaL ly thin the same and restricting the flow of metal outwardlytoward the periphery of the disk during the rolling operation by meansof a concavity formed in one of said dies. said concavity blendingsmoothly with the conour of the outer peripheral portions of the Intestimony whereof they hereunto aflix their Signature.

CAROLUS LEVON EKSERGIAN. EDWARD G. BUDD.

